brand logo

Why experts are proposing a third vaccine dose

11 Jul 2021

  • The higher infectivity of Lambda and its implications 

 By Buddhika Samaraweera   Although more than one-and-a-half years have passed since the outbreak of the Covid-19 pandemic around the world, given its new variants, which are reported from time to time, how long it would take to eradicate this pandemic is still anybody’s guess. The World Health Organisation (WHO) has divided the variants of the SARS-CoV-2 into two main categories: variants of concern and variants of interest. Accordingly, variants such as Alpha (B.1.1.7), Beta (B.1.351), Delta (B.1.617.2), and Gamma (P.1) have been designated as variants of concern, while the variants such as Eta (B.1.525), Iota (B.1.526), and Kappa (B.1.617.1) have been designated as variants of interest. The latest variant of SARS-CoV-2 – the Lambda variant or C.37 – has been designated by the WHO as a variant of interest, and the Health Ministry has recently stated that PCR test samples are currently being directed for gene sequencing to ascertain if anyone in the country has been infected with the latest variant, Lambda, and to take steps to inform the public immediately if such is the case. The Morning contacted the Professor and Consultant in Clinical Immunology and Allergy Prof. Suranjith Seneviratne, who is attached to the Institute of Immunity and Transplantation, Royal Free Hospital and University College, London, UK, and is the Consultant Speciality Lead of Immunology at the Health Services Laboratories, to inquire about some important matters pertaining to this new variant.   Variants of interest According to him, the WHO has so far identified seven variants of SARS-CoV-2 as variants of interest, the latest of which is the Lambda variant. It was first detected in samples obtained from Peru in December 2020 and was designated on 14 June as a variant of interest. Other notable variants of interest are the Eta variant, which was detected in many countries in December 2020 and designated as a variant of interest on 17 March 2021, the Iota variant which was detected in the US in November 2020 and designated as a variant of interest on 24 March 2021, and the Kappa variant discovered in India in October 2020 that was designated as a variant of interest on 4 April 2021. Prof. Seneviratne said that the Lambda variant has a unique pattern of seven mutations in the spike protein gene (the spike protein is on the surface of the virus and is needed for the virus to enter a cell). He noted that one of the mutations observed in the Lambda variant, known as L452Q, is very similar to the mutation L452R, which causes the rapid spread of the Delta variant of SARS-CoV-2. He said this is an important observation in relation to the Lambda variant.   Spread of the Lambda variant Commenting on the spread of the Lambda variant, Prof. Seneviratne said that this variant, which was first detected in Peru in December 2020, had spread significantly within that country by April 2021. Accordingly, by April 2021, more than 80% of the sequenced Covid-19 cases detected in Peru were found to be Lambda variant. By June, according to Prof. Seneviratne, it had begun to spread to other countries in South America, and by 14 June 2021, it had also spread to a number of other countries outside South America, resulting in its designation as a variant of interest by the WHO.  "By 15 June 2021, the Lambda variant had spread to 29 countries, and a strong presence was reported in South America," he added. According to reports, the Lambda variant of Covid-19 is currently prevalent in 29 countries, with the highest number of cases being reported in Chile as of 9 July 2021, at 862 (32% of the sequenced Covid-19 cases). There were 657 cases in the US, 328 in Peru (81% of the sequenced Covid-19 cases), 115 in Mexico, 100 in Germany, 87 in Argentina (37% of Covid-19 cases), 55 in Spain, 51 in Ecuador, 25 in Israel, 20 in Colombia, and 14 in France.  In addition, 11 cases of the Lambda variant of Covid-19 infection were reported from Italy, 10 from St. Kitts and Nevis, nine from Switzerland, eight from the UK, four each from Canada and Brazil, three from Poland, and two each from Aruba and Portugal. Also, as of 9 July, 2021, one Lambda variant Covid-19 case each has been detected from Bolivia, Uruguay, Turkey, Australia, Belgium, the Netherlands, Curacao, Denmark, and the Czech Republic. Adding that the Lambda variant has caused a number of problems in Peru, Prof. Seneviratne said that the world’s highest per capita death rate with regard to the Covid-19 pandemic, is currently being reported from Peru.   Is it more transmissible? According to Prof. Seneviratne, by December 2020, one out of every 200 SARS-CoV-2 samples from Peru was of the Lambda variant, which had then increased to 50% by March, and 80% by July 2021. However, it is yet to be ascertained whether this variant is more dangerous and studies are being carried out on this aspect, he added.   Vaccine effectiveness Elaborating on the effectiveness of the Covid-19 vaccine against the Lambda variant of SARS-CoV-2, Prof. Seneviratne said that two laboratory studies have so far been conducted on the efficacy of the Covid-19 vaccine against this strain. Accordingly, one study had been carried out by the University of Chile while the other one had been conducted by the NYU Grossman School of Medicine. “The study, conducted by the University of Chile, was done after obtaining plasma samples from health care workers who received two doses of the Sinovac (Coronavac) vaccine. The Lambda variant showed greater infectivity compared to both the Alpha and Gamma variants. Although both doses of the vaccine were received, the antibodies that were produced were less likely to neutralise the Lambda variant (that is, there was a threefold reduction in neutralisation),” he explained. He said this study suggested the Lambda variant was better able to escape antibodies produced by the Sinovac vaccine.  The other study, carried out using serum from individuals who had received either the Pfizer or Moderna vaccines, found the Lambda variant to be neutralised by vaccine-elicited antibodies  (with a 2.3-3.3-fold decreased titer) and convalescent sera. It was also neutralised by the Regeneron Monoclonal antibody (Mab) cocktail. He said the study also found the Lambda variant to show a twofold increase in infectivity (that was attributed to the L452Q mutation). Prof. Seneviratne mentioned that there has been much discussion about the reduced effectiveness of some of the inactivated vaccines. Some experts have proposed giving a third vaccine dose as a booster to improve the effectiveness, and this is currently being done in some Middle Eastern countries. He added that the Lambda variant has spread from South America to North America and Europe. Although no cases of the Lambda variant of SARS-CoV-2 have been reported in countries such as India and Sri Lanka, it is still important to be on the look-out for this variant, since some of the Covid-19 vaccines have been shown to be less effective against it.


More News..